1. Field of the Invention
The present invention relates to a relay or an electromagnetic relay configured to turn on and off a domestic or industrial electric apparatus.
2. Description of the Related Art
In an electromagnetic relay, under the condition that the voltage applied to a contact point formed by a fixed contact and a movable contact, which is opened and closed, is high and current flowing through the contact point is large, there is concern for generation of an arc when the voltage becomes higher than a minimum arc voltage or the current becomes larger than a minimum arc current at the time of the fixed contact and the movable contact in contact with each other moving away from each other with the movement of the movable contact in a direction away from the fixed contact or the fixed contact and the movable contact out of contact with each other moving toward each other with the movement of the movable contact in a direction toward the fixed contact.
With an electrical load applied between the fixed contact and the movable contact, electric current moves through the gap between the surface of the fixed contact and the surface of the movable contact. This phenomenon is referred to as an arc. The arc starts when electrons reach the positive terminal across the gap from the negative terminal. The electrons collide with and ionize molecules of air while moving through the gap. The electrons reach the positive terminal to heat the positive terminal, so that positive ions are released into the gap from the positive terminal. The positive ions collide with the negative terminal to heat the negative terminal as well.
Heat is thus generated at each of the positive terminal and the negative terminal to cause evaporation of molecules of the positive electrode and the negative electrode. As a result, the abrasion of the surfaces of the fixed contact and the movable contact increases, and the generation of the arc causes the electrically conducting state to continue at the time of interrupting electric current in particular, thus degrading interruption performance. Therefore, it is desired to suppress or extinguish the generated arc with efficiency in terms of both increasing the durability of the contacts and improving the interruption performance.
The above-described demand for arc suppression or extinguishing is particularly strong in the case of inserting a relay or an electromagnetic relay, in order to completely interrupt electric current, in a circuit containing an uninterruptible power supply (UPS) having the function of being activated to supply high-voltage direct-current (DC) power when a commercial power supply to a load such as a computer system fails or in a circuit containing a battery to supply DC power to a load such as an inverter in an electric vehicle.
For example, Japanese Laid-Open Patent Application No. 2001-176370 describes an electromagnetic relay capable of suppressing or extinguishing such an arc.